As disclosed in the patent documents listed below, there are known fuel cell systems that confine the fuel gas in a gas flow channel that is in contact with the anode in the power generating surface of the fuel cell (referred to as anode gas flow channel hereinafter) during operation (referred to as anode dead end system hereinafter). In the anode dead end system, impurities, such as nitrogen and water, are accumulated in the anode gas flow channel of the fuel cell during operation. If the impurities cover the surface of the membrane electrode assembly (MEA), the electromotive reaction on the electrode catalyst is inhibited, resulting in a decrease in voltage. In addition, the resulting abnormal potential can cause deterioration of the MEA. Thus, the conventional anode dead end systems open the exhaust valve at appropriate times to discharge the impurities accumulated in the anode gas flow channel to the outside of the system at the downstream end of the anode gas flow channel.
Patent document 1: JP-A-2005-353569
Patent document 2: JP-A-2005-353303
Patent document 3: JP-A-2005-243477
Patent document 4: JP-A-H9-312167